VIII Semester

ME 2041 - ADVANCED IC ENGINES

Part-A

UNIT - 1

1. What are the stages of combustion in a SI engines?

The stages of combustion in a SI engines are:

FIRST STAGE: Ignition lag (or)

preparation phase SECOND STAGE:

propagation of flame

THIRD STAGE: After burning

2. What are the various factors that affect the flame speed?

a) Turbulence b) F/A ratio c) T, P d) Compression ratio e) Engine

speed, size &

output

3. Define normal combustion?

In normal combustion, the flame initiated by the spark travels

across the combustion chamber in a fairly uniform manner.

4. Define abnormal combustion and its consequences?

Under certain operating conditions the combustion deviates from its

normal

Course leading to loss of performance and possible damage to the

engine are

termed as abnormal combustion (or) knocking combustion.

Consequences are (1).

Loss of power (2). Recurring preignition (3). Mechanical damage to

the engine

5. What is equivalence ratio?

The ratio of the actual fuel-air ratio to the stoichiometric fuel -air ratio.

6. Short note on SI engine equivalence ratio requirements?

1

In a homogeneous mixture with equivalence ratio close to 1.0 the flame

speed is normally of the order of 40cm/s .However in a SI engine the

maximum flame speed is obtained when φ is between 1.1 and 1.2 (i.e.)

when the mixture is slightly richer than stoichiometric.

7. Write the desirable qualities for SI engine fuel?

In order to avoid or inhibit detonation, a high auto ignition temperature

and a long ignition lag are the desirable qualities for SI engine fuel.

8. Explain the type of vibration produced when auto ignition occurs.

Two different vibrations are produced.

1. In one case, a large amount of mixture may auto ignite giving use

to a very

rapid increase in pressure throughout the chamber and

there will be a

direct blow on free vibration of the engine parts

2. In another case, larger pressure differences may exit in the

combustion chamber and the resulting gas vibration can force the

walls of the chamber to vibrate at the same frequency as the gas.

9. What is the method to detect the phenomenon of knocking?

The scientific method to detect the phenomenon of knocking is to use

a pressure transfer this transducer is connected, usually to a cathode ray

oscilloscope. Thus pressure-time traces can be obtained from the pressure

transducer.

10. List out some of the knock limited parameters?

The knock limited parameters are:

1. Knock limited compression ratio

2. Knock limited into pressure

3. Knock limited Indicated mean effective pressure. (Klimep)

11. Define performance number?

2

Performance number is defined as the ratio. Of Knock limited

Indicated mean effective pressure with the sample fuel to knock limited

Indicated mean effective pressure with ISO-OCTANE .when the inlet

pressure is kept constant.

12. List the factors that are involved in either producing (or) preventing

knock.

The factors that are involved in either producing (or) preventing

knock are temperature, pressure, density of the unburned charge and the

time factor.

13. List the parameters which are affecting knock in SI engine?

The parameters which are directly (or) indirectly connected with

knocking are

inlet temperature of mixture compression ratio, mass of inducted charge,

power output of the engine.

14. List the parameters in time factors that reduce the knocking?

Parameters are turbulence, engine speed, flame travel distance,

combustion chamber shape and location of spark plug.

15. List the composition factors in the knocking?

Air -fuel ratio and octane value of the fuel are the composition

factors.

16. What are the objectives to be kept in mind during design of

combustion chamber?

General objectives are

(a) Smooth engine operation (b) Moderate rate of

pressure rise

(c) Reducing the possibility of knocking (d) High power

out put and thermal efficiency

17. What are the factors to be considered to obtain high thermal

efficiency?

Following are the factors:

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1. A high volumetric efficiency. 2. Anti knock

characteristic must be

improved.

3. Compact combustion chamber reduces heat loss during

combustion increases

the thermal efficiency.

18. Write the different types of combustion chambering SI engine?

T-Head type, L- Head type, I- Head type, F- Head type.

19. What are the components required in the fuel injection system?

Components are -pumping element, metering element, mixing

element, distributing element, Timing control, and ambient control.

20. What are the advantages of fuel -injection in an SI engine?

Advantages are:

1. Increased volumetric efficiency. 2. Better thermal

efficiency

3. Lower exhaust emissions 4. High quality fuel

distribution.

21. List the drawbacks of the carburetion?

1. Non uniform distribution of mixture in multi cylinder engines.

2. Loss of volumetric efficiency due to retraction for mixture flow

and possibility of back firing.

22. What are the functional requirements of an injection system?

1. Accurate mixing of the fuel injected per cycle. 2. Timing the

injection of

the fuel.

3. Proper atomization of fuel into fine droplets 4. Proper spray

pattern.

5. No lag during beginning and end of injection.

23. List some of the important requirements of an automobile

carburetors?

1. Ease of starting the engine, particularly under low ambient

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conditions.

2. Good and quick acceleration of the engine.

3. Good fuel economy.

4. Ensuring full torque at low speeds.

24. What are the general types of carburetors?

Types are UPDRAUGHT, DOWN DRAUGHT, and CROSS

DRAUGHT.

25. What are the essential parts, compensating device and additional

system (modern) carburetors?

Parts - fuel strainer, float chamber, main metering and idling

system, the choke & the throttle. Compensating devise- Air -bleed jet,

compensating jet, Emulsion tube, auxiliary valve and port, back suction

control mechanism.

Additional system -Ant dieseling, richer coasting,

acceleration pump and economic (or) power enrichment system.

26. Define carburetion?

The process of formation of a combustible fuel -air mixture by

mixing the proper amount of fuel with air before admission to engine

cylinder is called carburetion.

27. What are the factors effecting carburetion?

1. The engine speed 2. The vaporization

characteristics

of fuel

3. The temperature of the in coming air 4. The design of the

carburetor

28. What are the different types air -fuel mixtures?

1.Chemically correct mixture 2. Rich mixture 3. lean mixture.

29. What are the different range of throttle operation

1. Idling 2. cruising 3. High power .

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UNIT - II

1. What are the stages of combustion in C.I engine?

The stages of combustion in C.I engine are four stages:

Stage I: ignition delay period (preparatory phase) combustion.

Stage 3: Period of controlled combustion. burning.

2. What is ignition delay period?

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Stage 2: Period of rapid

Stage 4: Period of after

The fuel does not ignite immediately upon injection into the

combustion chamber. There is a definite period of inactivity between the

time when the first droplet of fuel hits the hot air in the combustion

chamber and the time it starts through the actual burning phase. This period

is known as ignition delay period.

3. What are two delays occur in ignition delay period?

The two delays occur in ignition delay period are the physically delay

and chemically delay. Physical delay is the time between the beginning of

injection and the attainment of chemical reaction conditions. Chemical

delay is the reaction starts slowly and then accelerates until the

inflammation or ignition takes place.

4. List the factors affecting the delay period?

The factors affecting the delay period are:

1. Compression ratio. 2. Atomization of the

fuel.

3. Quality of the fuel. 4. Intake temperature

and pressure.

5. Explain the effect of quality of fuel factor on the delay period?

Self-ignition temperature is the most important property of the fuel

which affects the delay period. A lower self-ignition temperature and fuel

with higher cetane number give lower delay period and smooth engine

operation. Other properties of the fuel which affects the delay period are

latent heat, viscosity and surface tension.

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6. Give a comparative statement various characteristics that reduces

knocking in S.I and C.I engine (any four)?

S.NO CHARCTERISTICS S.I ENGINE C.I ENGINE

1 Ignition temperature of

fuel

High low

2 Ignition delay long short

3 Compression ratio Low high

4 Inlet temperature and

pressure

Low HIGH

7. Write the classification of combustion chamber in C.I engine?

Combustion chamber in C.I engine is classified into two categories:

1. Direct-injection type 2. Indirect-injection type.

8. What is called direct injection type of combustion chamber?

Direct injection type of combustion chamber is also called an open

combustion In this type the entire volume of the combustion chamber is

located in the main cylinder and the fuel is injected into this volume.

9. What are the types of open combustion chamber?

In open combustion chamber there are many designs some are

a. Shallow depth chamber b. Hemisherical chamber

c. Cylindrical chamber d. Toroidal chamber

10. What are the advantages and disadvantages of open combustion

chamber

type?

Advantages:

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1. Minimum heat loss during compression because of lower surface

area to volume

ratio

2. No cold starting problems

3. Fine atomization because of multihole nozzle

Disadvantages:

1. High fuel injection pressure required and hence complex design of

fuel injection

pump

2. Necessity of accurate metering of fuel by the injection system,

particularly for small engines.

11. What is indirect injection type of combustion?

Indirect injection type of combustion chamber in which the

combustion space is

divided in to two or more distinct compartment connected by restricts

passages. This

creates considerable pressure difference between them during the

combustion process.

12. Write the classification of indirect injection chamber (divided

combustion chamber)

Classification of divided combustion chamber is

a. Swirl chamber - in which compression swirl is generation.

b. Precombustion chamber - in which combustion swirl is induced.

c. Air cell chamber - in which both compression and combustion swirl are

induced.

13. What are the applications of swirl chamber?

Swirl chamber type finds application

a. Where fuel quality is difficult to control

b. Where reliability under adverse condition is more important than fuel

economy

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c. Use of single hole of larger diameter for the fuel spray nozzle is often

important consideration for the choice of fluid chamber engine.

14.) List the advantages and drawbacks of indirect

injection chamber:

Advantages:

1. Injection pressure required is low 2. Direction of spraying

is not very

important

Disadvantages:

1. Poor cold starting performance required heater plugs 2.

Specific fuel consumption is high

15. Why specific fuel consumption is high in indirect injection type

combustion chamber:

Specific fuel consumption is high because there is a loss of

pressure due to air motion through the duct and heat loss due to large heat

transfer area.

16. What is turbo charging?

Energy available in the engines exhaust gas is used to drive the the

turbocharger compressor, which raises the inlet fluid density prior to entry

to each engine cylinder. This is called turbo charging.

17. What are the major parts of a turbocharger?

The major parts of a turbocharger are turbine wheel, turbine housing,

turbo shaft, compressor wheel, compressor housing and bearing housing.

18. Explain the term turbo lag.

In case of turbo charging there is a phenomenon called turbo lag,

which refers to the short delay period before the boost or manifold pressure,

increase. This is due to the time the turbocharger assembly takes the exhaust

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gases to accelerate the turbine and compressor wheel to speed up.

19. Explain the function of waste gate.

In the turbocharger assembly there is a control unit called waste gate. It is a

diaphragram operated value that can bypass part of the gases around the

turbine wheel when manifold pressure is quite high this unit limits the

maximum boost pressure to prevent detonation in S.I engines and engine

damage.

20. Why there is a large pressure differences across the injector nozzle

are required:

The fuel is introduced in to the cylinder of a diesel engine through a

nozzle with a

large pressure differences across the nozzle jet will enter the chamber at

high velocity

to 1. Atomize in to small sized droplets to

enables rapid

evaporation and

2. Traverse the combustion chamber in the time available and fully utilize

the air

charge.

21. What is called break up length?

The liquid column bearing the nozzle disintegrates with in the

cylinder over a

finite

Length called the break up length in to drops of different sizes.

22. What are the different designs of nozzle used?

The different design of nozzle used is single orifice, multiorifice,

throttle or pintle depending on the needs of the combustion system

employed.

23. What are the two types of photographic technique used?

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To distinguish the liquid - containing core of the jet and the extracts of

the fuel vapor region of the spray, which surrounds the liquid core, two

types of photographic technique used are backlighting and shadow graph.

24. Explain photographic techniques method:

Back lighting identifies region where sufficient liquid fuel (as

ligaments or drops) is present to attenuate the light.

The shadowgraph technique responds to density gradients in the test

section so it identifies regions where fuel vapor exists.

25. List the droplet size depends on various factors:

The droplet sizes depends on various factors are

1. Mean droplet size decreases with increases in a. Injection

pressure

b. air density

2. Mean droplet size increases with increases in fuel viscosity.

3. Size of droplets increases with increases in the size of the orifice.

26. Define flame development angle:

The crank angle interval between the spark discharge and the time

when a small but significant fraction of the cylinder mass has burned or fuel

chemical energy has been released

27. Define rapid burning angle:

The crank angle interval required to burn the bulk of the charge is

defined as the interval between the end of the flame development stage and

the end of the flame propagation process.

UNIT - III

1. What are the major exhaust

emissions?

The major exhaust emissions

are

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a. Unburnt hydrocarbons (HC) b. Oxides of carbon (co

and co2)

c. Oxides of nitrogen (NO and NO2) d. Oxides of sulphur (SO2

and SO3)

e. Particulates f. Soot and smoke

2. What are the causes for hydrocarbon emission from

S.I engine The causes for hydro carbon emission from

S.I engine are

1. Incomplete combustion. 2. Crevice volume and flow in crevices. 3.

Leakage past the

exhaust valve. 4. Valve over lap. 5. Deposits on walls. 6. Oil on

combustion chamber

walls.

3. What are the reasons for incomplete combustion in SI engine?

Incomplete combustion is due to

a. Improper mixing due to incomplete mixing of the air and fuel. Some fuel

particles do not find the oxygen to react with this cause the emissions.

b. Flame quenching: As the flame goes very close to the walls it gets

quenched at the walls leaving a small volume of unreacted air fuel mixture.

4. What are the reasons for flame quenching?

The reason for flame quenching is the expansion of gases. (i) As

the piston

moves down from TDC to BDC during power stroke, expansion of the

gases lowers

both pressure and temperature with in the cylinder. This makes combustion

slow and

finally quenches the flame and causes the emissions. (ii) High exhaust

gas

contamination causes poor combustion and which in turn causes quenching

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during

expansion.

(iii) As the flame goes very close to the walls it gets quenched at the walls

leaving a small volume of unreacted air-fuel mixture.

5. How the oil consumption increases in IC engines and what are the

effects

Often as engines ages, due o wear, clearance between the pistons

and cylinder wall increases. This increases oil consumption contributes to

increases in the emissions in three ways.

a. There is an added crevices volume.

b. There is added absorption - desorption of fuel in the thicker oil film on

cylinder

walls

c. There is oil burned in the combustion process

6. Write a short note on carbon monoxide emissions

Carbon monoxide is a colourless and odourless but a poisonous gas.

It is

generated in an engine when it is operated with a fuel rich equivalance ratio.

Poormixing, local rich regions, and incomplete combustion will also be

the source for

co emissions.

7. What is photochemical smog?

NOx is the primary causes of photochemical smog, Smog is formed by

the

photochemical reaction of automobiles exhaust and atmosheric air in the

presence of

sunlight.

NO2 + energy from sunlight NO + O +smog

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8. What are soot particles?

Soot particles are clusters of solid carbon sheres. These spheres have

diameter from 9nm to 90nm (1nm = 10-9). But most of them are with in the

range of 15 -

30nm. The spheres are solid carbon with HC and traces of other

components absorbed on the surface. Single soot particles may contain up

to 5000 carbon spheres.

9. Which is the most effective after treatment for reducing engine

emissions

The catalytic converter is the most effective after treatment for reducing

engine emissions found on most automobiles. Co can be oxidized to CO2

and H2O in exhaust system and thermal converters if the temperature is held

at 600- 700C. If certain catalysts are present, the temperature needed to

sustain these oxidation processes is reduced to 250 - 300C, making for a

much more attractive system.

10. What is a catalyst?

A catalyst is a substance that accelerates chemical reaction by lowering

the energy needed for it to proceed. The catalyst is not consumed in the

reaction and so functions indefinitely unless degraded by heat age

contaminants or other factors.

11. List the materials used as catalyst

The catalyst materials most commonly used are a. platinum b.

palladium c. rhodium.

12. Why catalytic converter called as three way converters

Catalytic converters are called as three way converters because

they are used to reduce the concentration of CO, HC and NOx in the

exhaust.

13. What are the types of ceramic structure used in catalytic convertor?

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Inside the container is a process ceramic structure through which the

exhaust gas

flows.

a. The ceramic is a single honey comb structure with many flow passages.

b. Some converters use loose granular ceramic with the gas passing between

the packed

spheres.

14. List out the drawbacks of catalytic converters

a. Sulphur offers unique problems for catalytic converters some catalyst

promote the conversion of SO2 to SO3 which eventually converted to

sulphuric acid. This degreds the catalytic convertor and contributes to acid

rain.

b. Catalytic converters are not very efficient when they are cold. When an

engine is

started after not being operated for several hours it takes several minute for

the

converter to reach an efficient operating temperature called as cold start up

problem.

15. What are the methods of catalytic converters preheating?

The methods of catalytic converters preheating included the following

a. By locating the converters close to the engine b. By having

superinsulation

c. By employing electric preheating d. By using flame heating e.

Incorporating

thermal batteries.

16. List the invisible and visible emission

Invisible emission: Water vapour, carbon dioxide, oxides of nitrogen,

unburnt hydrocarbons, carbon monoxide, aldehyes.

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Visible emission: Smoke, particulate.

17. What are the methods of measuring the following emission?

a. Oxides of nitrogen = CHEMILUMINESCENCE ANALYZER

b. Carbon monoxide = NON DISPERSIVE INFRARED

ANALYZER

c. Unburned hydrocarbons = FLAME IONIZATION DETECTOR

(FID)

UNIT-IV

1. Write the advantage and disadvantage of alcohol as a fuel?

The advantages of alcohols a fuel are:

1. it is a high octane fuel with antiknock index number (octane number) of

over 100.

2. Alcohols have low sulphur content in the fuel.

3. It produces less overall emissions when compared

with gasoline Disadvantages:

1. Alcohols have poor ignition characteristics in general.

2. There is a possibility of vapor lock in fuel delivery system.

3. It has poor cold weather starting characteristics due to low vapor pressure

and evaporation.

2. What is the problem with gasoline-alcohol mixture as a fuel?

Problems with gasoline-alcohol mixture as a fuel are the tendency for

alcohol to combine with any water present. When this happens the alcohol

separates to locally from the gasoline, resulting in a non-homogenous

mixture. This causes the engine to run erratically due to the large air-fuel

ratio difference between the two fuels.

3. Write the sources for methanol?

Methanol can be obtained from many sources, both fossil and renewable.

These include coal, petroleum, natural gas, biomass, wood landfills and

even the ocean.

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4. Write the source for ethanol?

Ethanol can be made from ethylene (or) from fermentation of grains and

sugar. Much of it is made from sugarcane, sugarbeets, and even cellulose

(wood and paper).

5. What are the techniques of using alcohol in diesel engine fuel?

The techniques of using alcohol in diesel engine are:

1. Alcohol diesel emulsions. 2. Dual fuel injection.

3. Alcohol fumigation. 4. Surface ignition of alcohols.

6. What are the methods are adopted for induction of alcohol into

intake manifold?

The methods are adopted for induction of alcohol into intake manifold

micro fog unit, pneumatic spray nozzle, vaporizer, carburetor and fuel

injector.

7. List the advantages of hydrogen as an IC engine?

Advantages

1. Low emissions.

2. Fuel availability.

3. Fuel leakage to environment is not a pollutant

4. High energy continent per volume when stored as a liquid.

8. List the disadvantages of using hydrogen as a fuel?

Disadvantages

Difficult to re fuel.

Fuel cost would be high at present day’s technology and

availability. Poor engine volumetric efficiency.

High NOx emission because of high flame.

9. Write the methods for hydrogen can be used in SI engines?

Hydrogen can be used in SI engines by

three methods

By manifold induction

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By direct introduction of hydrogen into

the cylinder. By supplementing

gasoline.

10. List the advantages and disadvantages of natural gas?

Advantages:

Octane number is around 120, which makes it a very good SI

engines fuel. Low engine emissions

Fulel is fairly abundant

worldwide. Disadvantages:

Low energy density resulting in low engine performance.

Low engine volumetric efficiency because it is a

gaseous fuel. Refueling is a slow process.

11. Write the two types of LPG used in automobiles engine?

Two type of LPG used in automobile engines:

One is propane and the other is butane, sometimes in mixture of

propane and butane is used as LPG in auto mobile engine.

12. What are the advantages of LPG?

LPG mixes with air at all

temperatures.

LPG has high antiknock

characteristics.

There is no crack case dilution, because the fuel is in the form of

vapor.

13. Write the disadvantages of LPG?

A special fuel feed system is required for liquid

petroleum gas. A good cooling system is quite

necessary.

The vehicle weight is increased due to the use of heavy pressure

cylinder for

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storing LPG.

14. Write the improvements required for the LPG vehicle in future?

Effort must be made to have more LPG filling stations at convenient

locations,

so that LPG tank can be filled up easily.

Safety devices are to be introduced to prevent accidents due to

explosion of gas

cylinders (or) Leakage in the gas pipes.

15. Compare the petrol and LPG?

PETROL LIQUIED PETROLEM GAS

Octane rating of petrol is 81 Octane rating of LPG is 110.

Petrol has odours LPG is odourless.

In order to increase octane number LPG is lead free with high Octane

number.

UNIT-V

1. What is lean burn engine?

Lean burn engine is a lay out of Otto cycle engine designed to permit the

combustion of

lean air fuel mixture and to obtain simultaneously low emission values as

high fuel

economy. It is designed to operate effectively in the air fuel ratio

14:1-16:1to 20:1-

22:1. When the lean compression ratio, combustion chamber shape, ignition

system,

the lean limit are successfully optimized, the engine is refused to as a lean

burn engine.

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2. Why lean mixture is preferred in SI engine?

Lean mixture is preferred in SI engine because of the

following facts:

Lower pollutants.

Good fuel economy.

Heat transfer losses to the cooing medium are reduced because of

lower peak

temperatures.

Since lean mixture are less prove to knocking.

3. What are the modifications to be made to convert an existing engine

as a lean burn engine?

The modifications to be made to comments an existing engine as a lean burn

engine

are:

Increasing the compression ratio of the engine to accurate flame

propagation.

Increasing the swirl and turbulence of the mixture in order to

increase flame

speed.

Catalytic activation of the charge in the combustion chamber.

4. How the stratified charge engine can be characterised?

The stratified charge engine can be characterised by the following features:

Relatively high compression ratio

Ability of direct cylinder fuel injection variations to run unthrottled.

Stratification of the charge mixture into distinctly different rich and

lean air fuel

ratios.

5. List the advantages of the stratified charge engine.

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The advantages of the stratified charge engines are:

Low octane fuels (cheaper fuels) can be used at higher

compression ratios.

Load control can be achieved without air throttling

Quiet in operation.

Multi fuels give more or less equal performance.

6. What are the main disadvantages of the stratified charge engine?

The main disadvantages of the stratified charge engines are:

Maximum output (from the air in the cylinder (i.e.) complete

utilization of air) is

not achieved.

The added cost of the injection/modified

combustion systems.

Added complication of injection and spark

ignition systems.

7. Write short notes on plasma jet ignition system.

The plasma jet ignition system uses a plasma jet spark plug. This system can

be

considered as a form of electrical torch ignition, since the ignition source is

hot jet

plasma which project well away from the spark plug. The plasma jet

ignition sources is

turbulent and electrodeless, both desirable features for igniting marginal

mixtures.

8. What are the factors that influence the operation of the plasma jet

plug?

The factors that can influence the operation of the plasma jet plug are the

amount of the

applied electrical energy, the rate of energy delivery, the cavity volume, the

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cavity

dimensions, the orifice size, the ambient gas pressure and the quantity of

fuel present in

the cavity.

9. What are the reasons for automotive engines equipped with

gasoline injection

system?

Some of the recent automotive engines are equipped with gasoline injection

system,

instead of a carburetion for the reasons: (1) To have uniform distribution of

fuel in a

multi cylinder engine. (2) To improve breathing capacity (i.e.) volumetric

efficiency.

(3) To reduce or eliminate detonation.

10. What are the types of injection systems?

1. Gasoline Direct Injection (GDI) in to the cylinder

2. Port injection (a) timed (b) continuous

3. Manifold injection

11. What are the objective of the fuel injection system?

The objectives of the fuel injection system are to meter, atomize and

uniformly distribute the fuel throughout the air mass in the cylinder.

12. What are the components of

injection system? The components of

injection system are:

1. Pumping element 2. Metering element 3. Mixing

element

4. Mixture control 5. Timing control

13. Write notes on continuous injection system.

Continuous injection system usually has a rotary pump. The pump

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maintains the fuel line gauge pressure of about 0.75 to 1.5 bar. The system

injects the fuel through a nozzle located in manifold immediately down

stream of the throttle plate.

14. Explain the functions of the following components.

(a) Pumping element, (b) Metering element, (c) Timing control, (d)

Ambient

control.

(a)Pumping element- moves the fuel from the fuel tank to the injector. This

include necessary piping, filter etc.

(b)Metering element- measures and supplies the fuel at the rate demanded

by load and speed conditions of the engine.

(c)Timing control- fixes the start and stop of the fuel-air mixing process.

(d)Ambient control-compensates for charges in temperature and pressure

of either air or fuel that may affect the various elements of the system.

15.Write the advantages of homogeneous charge compression ignition

engine?

1. Lower NOx and particulate emissions 2. High thermal

efficiency

16. What are the fuels used in HCCI engines?

Diesel , gasoline , methanol , natural gas and hydrogen

17. List the disadvantages of homogeneous charge compression

ignition engine?

The major problem is controlling the ignition timing over a wide

lead and speed.

Power density is limited by combustion noise and high peak

pressure.

Part- B

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UNIT- I

1. Discuses why a modern carburetor is being replaced by an injection

system in SI

engine?

2. Explain the factors that affect the process of carburetion?

3. What are different air -fuel mixture on which an engine can be operated?

4. Explain the following1. Rich mixture, 2. Stoichiometric mixture 3. Lean

mixture.

5. How the power and efficiency of the SI engine vary with air- fuel ratio

for

different load and speed conditions?

6. By means of suitable graph explain the necessary carburetor performance

to fulfill

engine requirements?

7. Explain why a rich mixture is required for the following 1. Idling 2.

Maximum power

and sudden acceleration.

8. Describe briefly the MPFI system with a neat sketch?

9. Explain port injection and throttle body injection system?

10.Describe D- MPFI and L-MPFI injection system?

11.Briefly explain the stages of combustion in SI engines elaborating the

flame front

Propagation

12.Explain the various factors that influence the phenomena of knock in SI

engines?

13.Explain the effete of various engine variables on SI engine knock.

14.What are the various types of combustion chamber s used in SI engines?

Explain

them briefly?

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UNIT - II

1. Bring out clearly the process of combustion in CI engines and also

explain the various

stages of combustion. What is delay period and what are the factors that

affect the

delay period?

2. Explain with figures various types of combustion chambers used in CI

engines.

3. Explain Turbo charging in CI engines.

4. Explain with heat sketch about the air vition

5. What are the effects of trubocharging on CI engines?

6. Compare induction swirl with compression swirl with respect to their

advantages and

disadvantages.

7. What are the main factors affecting the penetration of the fuel spray in CI

engines?

8. Explain about the fuel spray behavior?

UNIT III

1. Describe in detail the causes of hydrocarbon emissions from SI engines.

2. What are catalytic converters? How are they helpful in reducing HC, CO

and NOx

emissions?

3. Give a brief account of emissions from CI engines.

4. Explain the internationally accepted methods of measuring the following

invisible

emission

5. i) Oxides of nitrogen (ii) Carbon monoxide (iii) Unburned

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hydrocarbons

6. What is smoke and classify the measurement of smoke?

UNIT - IV

1. Explain the reasons for looking for alternate fules for IC engines.

2. Explain alcohols as alternate fuels for IC engines bringing out their

merits and

demerits.

3. Explain the possibility of using reformulated gasoline and water

gasoline mixture as

alternate fuel.

4. Can alcohol be used for CI engines ? Explain.

5. Explain with a neat sketch the surface-ignition alcohol engine.

6. What are the advantages and disadvantages of using hydrogen in SI

engine.

7. Explain the two methods by which hydrogen can be used in CI engine.

8. What is natural gas? List the advantages and disadvantages of using

natural gas as

alternate fuels?

9. Give a brief account of LPG being used as an alternate fuel in SI engine?

10.What are the advantages and disadvantages of using LPG in SI engines?

11.Compare LPG and petrol as fuel for SI engines.

UNIT - V

1. What is the necessity for gasoline injection? Explain with suitable sketch.

2. With neat sketch, explain the exhaust emissions with different air-fuel

ratio lean burn

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spark ignition engines.

3. What do you understand by charge stratification? Explain the method of

achieving the

same with suitable sketches. Discuss the advantages and disadvantages

of charge

stratification.

4. Explain briefly plasma - jet ignition system.

5. What is a learn burn engine? What are the advantages of using learn

mixture in SI

engine?

6. Explain the characteristics of Homogeneous charge compression ignition

engine.

7. Explain gasoline direct injection engine.

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